Ansar Maria, Serrano Daniel, Papademetriou Iason, Bhowmick Tridib Kumar, Muro Silvia
Institute for Bioscience and Biotechnology Research, University of Maryland , College Park, Maryland 20742, United States.
ACS Nano. 2013 Dec 23;7(12):10597-611. doi: 10.1021/nn404719c. Epub 2013 Nov 20.
Targeting of drug carriers to cell-surface receptors involved in endocytosis is commonly used for intracellular drug delivery. However, most endocytic receptors mediate uptake via clathrin or caveolar pathways associated with ≤200-nm vesicles, restricting carrier design. We recently showed that endocytosis mediated by intercellular adhesion molecule 1 (ICAM-1), which differs from clathrin- and caveolae-mediated pathways, allows uptake of nano- and microcarriers in cell culture and in vivo due to recruitment of cellular sphingomyelinases to the plasmalemma. This leads to ceramide generation at carrier binding sites and formation of actin stress-fibers, enabling engulfment and uptake of a wide size-range of carriers. Here we adapted this paradigm to enhance uptake of drug carriers targeted to receptors associated with size-restricted pathways. We coated sphingomyelinase onto model (polystyrene) submicro- and microcarriers targeted to clathrin-associated mannose-6-phosphate receptor. In endothelial cells, this provided ceramide enrichment at the cell surface and actin stress-fiber formation, modifying the uptake pathway and enhancing carrier endocytosis without affecting targeting, endosomal transport, cell-associated degradation, or cell viability. This improvement depended on the carrier size and enzyme dose, and similar results were observed for other receptors (transferrin receptor) and cell types (epithelial cells). This phenomenon also enhanced tissue accumulation of carriers after intravenous injection in mice. Hence, it is possible to maintain targeting toward a selected receptor while bypassing natural size restrictions of its associated endocytic route by functionalization of drug carriers with biological elements mimicking the ICAM-1 pathway. This strategy holds considerable promise to enhance flexibility of design of targeted drug delivery systems.
将药物载体靶向参与内吞作用的细胞表面受体常用于细胞内药物递送。然而，大多数内吞受体通过与直径≤200纳米囊泡相关的网格蛋白或小窝途径介导摄取，限制了载体设计。我们最近发现，细胞间黏附分子1（ICAM-1）介导的内吞作用不同于网格蛋白和小窝介导的途径，由于细胞鞘磷脂酶被募集到质膜，使得纳米和微载体能够在细胞培养和体内被摄取。这导致在载体结合位点产生神经酰胺并形成肌动蛋白应力纤维，从而实现对各种大小范围载体的吞噬和摄取。在此，我们采用这种模式来增强靶向与大小受限途径相关受体的药物载体的摄取。我们将鞘磷脂酶包被在靶向与网格蛋白相关的甘露糖-6-磷酸受体的模型（聚苯乙烯）亚微载体和微载体上。在内皮细胞中，这使得细胞表面神经酰胺富集并形成肌动蛋白应力纤维，改变摄取途径并增强载体的内吞作用，而不影响靶向、内体运输、细胞相关降解或细胞活力。这种改进取决于载体大小和酶剂量，对于其他受体（转铁蛋白受体）和细胞类型（上皮细胞）也观察到了类似结果。在小鼠静脉注射后，这种现象还增强了载体在组织中的积累。因此，通过用模拟ICAM-1途径的生物元件对药物载体进行功能化，有可能在绕过其相关内吞途径的天然大小限制的同时，保持对选定受体的靶向性。这种策略对于增强靶向药物递送系统设计的灵活性具有很大的前景。
